[jira] [Created] (IMPALA-11127) Document the UTF8_MODE query option and relavent string functions

["Quanlong Huang (Jira)" <ji...@apache.org>]

Quanlong Huang created IMPALA-11127:
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             Summary: Document the UTF8_MODE query option and relavent string functions
                 Key: IMPALA-11127
                 URL: https://issues.apache.org/jira/browse/IMPALA-11127
             Project: IMPALA
          Issue Type: Documentation
    Affects Versions: Impala 4.1.0
            Reporter: Quanlong Huang
            Assignee: shajini thayasingh


Since IMPALA-2019 is resolved, we can document the UTF8_MODE query option added in it now. The query option will turn on the UTF-8 aware behavior of string functions. The relevant string functions and their UTF-8 aware behaviors are:
 * LENGTH(STRING a)
 ** returns the number of UTF-8 characters instead of bytes
 * SUBSTR(STRING a, INT start [, INT len])
SUBSTRING(STRING a, INT start [, INT len])()
 ** the substring start position and length is counted by UTF-8 characters instead of bytes
 * REVERSE(STRING a)
 ** the unit of the operation is a UTF-8 character, ie. it won't reverse bytes inside a UTF-8 character.
 * INSTR(STRING str, STRING substr[, BIGINT position[, BIGINT occurrence]])
LOCATE(STRING substr, STRING str[, INT pos])
 ** These functions have an optional position argument. The return values are also positions in the string. In UTF-8 mode, these positions are counted by UTF-8 characters instead of bytes.
 * mask functions
 ** The unit of the operation is a UTF-8 character, ie. they won't mask the string byte-to-byte.
 * upper/lower/initcap
 ** These functions will recognize non-ascii characters and transform them based on the current locale used by the Impala process.



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